The present invention relates generally to ground run-up enclosures (GRE) used to reduce the noise created by high power maintenance operations by jet and turboprop aircraft. These facilities are also know as engine ground run pens (GRP), Run-up facilities (RUF) and hush houses. This invention relates particularly to ground run up facilities utilizing a separate jet blast deflector located ahead of the rear wall and having a vented rear wall. Jet blast deflectors are also known as jet blast fences or jet blast screens. The present invention is for a ground run-up enclosure utilizing a separate jet blast deflector located ahead of a vented rear noise wall. This design allows the separate jet blast deflector to be located close to the noise attenuating rear wall by providing a vent in the rear noise attenuating wall to provide a mixing air source for the high velocity air discharged at the discharge lip of the jet blast deflector. This allows the overall length of a traditional ground run-up enclosure utilizing a separate jet blast deflector to be reduced and improves airflow within the facility. This system may be used to provide noise attenuation for various types of jet and turbo prop aircraft testing. The structure has a jet blast deflector located ahead of a rear noise attenuating wall that is vented to allow mixing airflow to be drawn to the discharge lip of the jet blast deflector.
High power engine run-ups on the ground at many airports have led to issues with the noise created by the aircraft engines operating at high power levels often for sustained periods. Nearby residential and commercial areas are sensitive to the high noise levels created.
Over the past twenty five years or so, ground run-up enclosures have developed into large, complex structures which surround the test aircraft with tall noise attenuating walls. They are typically built with separate jet blast deflectors located ahead of the rear noise wall to deflect the jet blast out of the structure. The jet blast deflectors are typically located well ahead of the rear wall to provide a source for mixing air to enter the rear of the facility. In view of the size of modern aircraft and the powerful engines used to power them, the jet blast deflectors inside a ground run-up enclosure must be tall enough and strong enough to withstand jet blasts at heights of up to approximately 25 feet or more. Different types of blast structures that are known to deflect aircraft exhaust flow and/or reduce noise associated with such exhaust flows are shown, for example, in: (1) U.S. Pat. No. 5,127,609 to Lynn, issued Jul. 7, 1992; (2) U.S. Pat. No. 5,429,324 to Lynn, issued Jul. 4, 1995; and (3) U.S. Pat. No. 5,865,640 to Lynn, issued Jan. 5, 1999.
High power ground testing of modern era aircraft with residential and other noise sensitive areas nearby gave rise to the need to provide noise attenuation. Airport operational aprons are extremely crowded due to the increase in the numbers of air travelers both for personal and business purposes, and due to the increased use of air freight to transport all types of goods. The use of airport resources by all types of aircraft is currently at an all time high and expected to continue to rise. In addition, as airports have grown and become busier, so has the demand for noise sensitive uses of the areas immediately surrounding the airports. With the demand for airport resources and real estate in high-growth mode, using the space on airports as efficiently as possible has become a significant challenge. For these reasons, it is desirable to have ground run-up enclosures that are more compact in size while still being able to operate in a variety of wind conditions and to do so while reducing noise associated with the high power aircraft engine operation in a highly efficient manner.
Ground Run-Up Enclosures comprising three or four sides with or without a roof are most commonly used to mitigate the noise created by high power engine ground run-ups and other aircraft maintenance procedures. Some GRE's can use a single surface straight, angled or curved rear noise attenuating wall without a separate jet blast deflector to deflect the jet blast. This single surface combined jet blast deflection surface and noise attenuating rear wall can be extremely aerodynamically inefficient, especially when the aircraft is surrounded by tall noise attenuating walls. The effect being a loss of momentum in the high velocity engine exhaust airflow resulting in a buildup of pressure at the rear wall. Recirculation of airflow within the facility results in decreasing the rearward momentum of the airflow within the ground run-up enclosure and also reduces the discharge velocity and angle of the deflected engine exhaust airflow out of the facility. In this aerodynamically inefficient configuration utilizing a combined jet blast deflector and rear noise wall, the mixing region between the high velocity flow up the deflecting surface and the ambient air must occur above the noise wall and noise created in this mixing region cannot be contained by the noise attenuating wall.
Other issues arise with respect to ground run-up enclosure designs which do not use a separate jet blast deflector, such as for example, noise being reflected by solid surfaces of the noise attenuating wall used to deflect the high velocity engine airflow. This reflected noise is directed out the front of the facility off of the solid rear wall surface. It is possible to acoustically treat these rear noise attenuating wall surfaces used to redirect jet blast, but such acoustic treatments are costly, inefficient and require a great deal of maintenance. Also in this design the mixing region of the airflow occurs above the top of the wall which means that any sound treatment applied to the wall would not reduce noise generated by the mixing airflows above the wall.
Many ground run-up enclosure designs utilize a separate jet blast deflector ahead of the rear noise attenuating wall to deflect the high velocity engine airflow up and out of the facility. In this design ambient air must mix with the high speed flow off of the discharge of the jet blast deflector surface. These ground run-up enclosure designs place the separate blast deflector well ahead of the tall rear noise attenuating rear wall to allow for a source for the mixing ambient airflow. Using a large open area between the jet blast deflector and the rear noise attenuating wall may create an unstable aerodynamic condition.